1. Field of the Invention
The present invention relates to invention is relative to a drive arrangement for a vehicle, especially a non-railborne vehicle, with at least one internal combustion engine, at least one generator, at least one electric drive motor and at least one torque converter arranged between the drive motor and a driven shaft as well as to a method for increasing the torque transferred onto the vehicle axles of a non-railborne vehicle with diesel-electric drive.
2. Description of the Related Art
The use of drives in which an internal combustion engine is connected to a generator for the production of current and in which the drive is brought about by an electromotor fed by said generator is currently being increasingly discussed, especially for street vehicles. Particular attention is to be called here to the so-called diesel-electric drives.
Such a diesel-electric drive is known for a non-railborne vehicle, for example, from European patent EP 0,527,145 B1. The vehicle known from this publication is distinguished in that the internal combustion engine and the generator are combined to a so-called internal combustion engine-generator subassembly.
Special drive concepts for vehicles with an internal combustion engine and a generator in which so-called permanent-magnet motors are used as drive motors are known from xe2x80x9cDrive Systems with Permanent Magnet Synchronous Motorsxe2x80x9d in Automotive Engineering, February, 1995, pp. 75-81.
The use of diesel-electric drives, especially in commercial vehicles, is described in the publication, xe2x80x9cAn Electrical Individual-Wheel Drive for City Busses of the Futurexe2x80x9d, B. Wxc3xcst, R. Mxc3xcller, A. Lange in Local Service, June/1994, Alba Fachverlag, Dusseldorf, pp. 1-7. The disclosed content of all previously cited publications is included herewith to its complete extent in the present application.
The drive motors and traction motors were always arranged close to the wheels in the drive arrangements known from the state of the art, especially in the form of the last-cited publication. This entailed a great number of disadvantages. For example, such drive arrangements were quite heavy and the vehicles deviated significantly in their design from traditional vehicles with conventional drive so that there was no compatibility.
These disadvantages can be overcome by a central drive in which the traction motors are not mounted on the axle close to the wheels or in the same axle, but rather are coupled to the axis via a summation transmission. In such an arrangement the traction motor can be attached in the chassis of, e.g., a city bus and drive a customary mechanical low-platform axle by means of a universal-joint shaft. This can reduce to a minimum the construction differences of a vehicle with a diesel-electric drive in comparison to a vehicle with an automatic transmission, which brings about significant logistic advantages.
A further disadvantage of the previous drive concepts was the fact that more than one traction motor always had to be used, e.g., two traction motors attached close to the wheels using the concept known from B. Wxc3xcst, R. Mxc3xcller, A. Lange: An Electrical Individual-Wheel Drive for City Busses of the Future, Der Nahverkehr, June/1994, pp. 1-7, Aba Fachverlag Dusseldorf. This was disadvantageous in particular in the case of permanently excited traction motors, which also include the transversal flux machines used as a motor. When two traction motors were used, very great no-load losses had to be overcome, which appear on account of the permanent excitation of the traction motors. A minimizing of the no-load losses might be possible if only one central traction motor is provided instead of, e.g., two traction motors.
The problem of the central drive concepts addressed is the fact that when only a single, central traction or drive motor is used during starting, only an insufficient torque is made available on the axles from the traction motor.
This problem is solved in accordance with the invention in that the drive motor or traction motor is coupled to a torque converter for magnifying the torque delivered from the drive motor onto the vehicle axles.
The torque output from the drive motor can be converted and magnified by connecting in a torque converter between the drive motor and the driven shaft. This is especially necessary during the starting of the vehicle in order to make available the required torques and starting traction. The same applies to use on inclines.
It is especially advantageous if the drive motor is not constantly connected to the converter but rather can be coupled to the converter and decoupled from it as required with the aid of a coupling. Any type of coupling is suitable for this purpose, e.g., those shown in Dubbel, xe2x80x9cPocket Book for Machine Constructionxe2x80x9d, 18th edition, pages G63-G74. The disclosed content of the previously cited publication is included to its full extent in this application. Converter bridge couplings and so-called lock-up couplings, which couple the converter to the traction motor as required and, when a torque conversion is no longer required, bridge the torque converter. Such converter bridge couplings or lock-up couplings are known in particular for hydrodynamic torque converters and shown, e.g., in Gerigk, Bruhn, Danner, Endruschat, Gobert, Gross, Komoll, Motor Vehicle Technology, Westermann Verlag, 2nd edition, 1994, pp. 349-352, the disclosed content of which is completely included in this application. In a hydrodynamic torque converter with bridge coupling or lock-up coupling, the converter operates with open coupling, that is, the converter is connected into the power flow from the drive motor to the driven shaft, whereas, on the other hand, when the coupling is closed the converter is bridged, so that the drive motor acts directly on the driven shaft.
A special embodiment provides that the drive arrangement comprises a control with whose aid it is possible that the converter is coupled to the drive motor when starting procedures are detected and when a set travel speed and/or starting acceleration is exceeded the control bridges the torque converter and separates it from the drive motor so that the drive motor then acts directly on the driven shaft and drives the vehicle. Thus, the torque converter operates only in the lower speed range and compensates, by means of the achievable magnifying of the torque, the disadvantage of the too slight torque of the electrical drive machine in this operating state. As a result of the monitoring of the starting acceleration by means of the control of the invention, the converter is only utilized for a rather long time period in very few instances of starting procedures. A torque conversion for a rather long time period is required in particular when starting on inclines, e.g., on inclines greater than 6 percent, with a fully occupied vehicle. In all other starting instances, the lock-up coupling is already closed in a short time so that losses, which can occur as a consequence of the converter output, remain without noticeable effects on the fuel consumption of the vehicle equipped with a torque converter. I this manner, it is achieved that the consumption advantage which can be achieved with a diesel-electric vehicle is preserved.
A hydrodynamic torque converter like the one disclosed, e.g., in xe2x80x9cHydrodynamic Transmissions, Couplings and Brakesxe2x80x9d, Krausskopf-Verlag GmbH, Mainz, 1970 on pages 28-37 is used with preference as a torque converter. A hydrodynamic torque converter comprises, in addition to a pump impeller and a turbine wheel, a guide wheel, which is also designated as a reaction component. Since the guide wheel of a torque converter must receive a moment as a reaction component and since the sum of the moments in the circuit must be equal to zero, the turbine moment can be greater than, equal to or less than the pump moment, depending on the magnitude and direction of rotation of the guide-wheel moment, that is, the pump moment can therefore be converted.
A drive arrangement in which the drive motor is arranged in the vehicle chassis is especially preferred. It is advantageous if a so-called central motor arrangement is selected for such an arrangement. Moreover an advantageous embodiment can provide that the generator and the drive motor are combined to an electrical transmission unit. This establishes the greatest possible compatibility with traditional drives. The drive train corresponds in its design to that of a conventional vehicle and the electrical transmission unit composed of generator and drive motor can take the place of the conventional transmission.
The use of so-called transversal flux machines as electrical drive motors is especially preferred. Such transversal flux machines are described, e.g., in the publication xe2x80x9cAn Electrical Individual-Wheel Drive for City Busses of the Futurexe2x80x9d, B. Wxc3xcst, R. Mxc3xcller, A. Lange in Local Service, June/1994, Alba Fachverlag, Dusseldorf, pp. 1-7. The content of this article is included herewith to its complete extent in the disclosed content of the present application.
In addition to the drive arrangement, the invention also makes available a method of increasing the torque transferred onto the vehicle axles of a non-railborne vehicle with diesel-electric drive. According to the method of the invention a start process of the non-railborne vehicle is detected. If such a start process is signaled to the control, the latter brings about the connecting of a torque converter to the drive motor. As a result of the coupling in of the torque converter into the drive train between the drive motor and the driven shaft, the torque made available from the drive motor is converted into a higher starting moment. For example, as a result of such a conversion of moment the torque on the driven shaft can be twice as great as the input moment made available from the drive motor. The travel speed and the vehicle acceleration are determined with the aid of sensors. If a given value for the travel speed or the starting acceleration is achieved, a signal is transmitted in turn to the control unit. This signal causes the control unit to decouple the torque converter from the drive motor or to bridge it so that the drive motor acts directly on the driven shaft. The time in which the conversion of moment is active during the starting process is set by the appropriate selection of the previously determined vehicle speed value or vehicle acceleration value. These parameters can be very readily optimized by an expert in the art without inventive activity as regards the starting moments required for different incline stretches and as regards the fuel consumption.